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Energy from waste David Scheeres
David.Scheeres@aspen-waite.co.uk
Aspen Waite Sustainable Energy Ltd (AWSE) was incorporated on November 6th 2020 to make a profit from the development and production of an innovative Anaerobic Digestion system. Anaerobic digestion is a process through which bacteria break down organic matter—such as animal manure, wastewater biosolids, and food wastes—in the absence of oxygen. Anaerobic digestion for biogas production takes place in a sealed vessel called a reactor, which is designed and constructed in various shapes and sizes specific to the site and feedstock conditions. These reactors contain complex microbial communities that break down (or digest) the waste and produce resultant biogas and digestate (the solid and liquid material end-products of the AD process) which is discharged from the digester. The illustration on the right shows how this works.
Why would a firm of accountants involve themselves in Anaerobic Digestion? The road to Aspen Waite Sustainable Energy began 15 years ago at a Recycling and Waste Management exhibition at the NEC. An enthusiastic young graduate, Waqas Ahmed explained his vision
to me for small portable digestion plants and was seeking technical assistance on heating and the recycling of plastics, two fields I am involved in. Over the years Waqas reappeared many times requesting technical and business advice and on some occasions, to commiserate with him regarding problems with nonperforming investors. It is said that invention is 5% inspiration and 95% perspiration and in Waqas’ case this has proved to be true. Waqas’ idea was to develop a portable digestion system which would have the advantage of not requiring solid foundations that a fixed plant would require. Planning permission is required for static AD plants and is often contentious and can take several years but a modular system does not need planning and as a consequence can be deployed where needed. To make them economically viable, large scale digestion plants require a large throughput of waste and the cost of transporting waste can be significant. There is a sensitive balance between cost of feedstock and value of the digestate. In respect of the Aspen Waite system, the plant is small scale so it is taken to the point of generation of waste and scaled to suit. I have long advocated dealing with recycling problems at source as transportation is expensive and not sustainable.
